Analog input devices for inputting information into a computer are used to enter discrete information by pressing, for example, discrete, binary keys. Also, analog input devices may be used as pointing devices to enter one or more channels of analog information, such as, for example, information relating to the force applied to an analog pointing device, such information to be used, for example, to control the position or velocity of a cursor on an associated computer monitor screen.
The present invention relates specifically to analog input devices for performing a class of mixed tasks in which an operator wishes to enter both discrete information by pressing discrete binary keys and, at almost the same time, or in rapid alternation, to enter one or more channels of analog information. Typical examples of such a class of mixed tasks include:
1. text editing on a computer, alternating focusing on a point on the screen with entering or deleting text at that point.
2. air traffic control-like applications, in which a point on the screen is selected for read-out or entry of data.
3. menu-driven computer applications, in which selection from a menu alternates with selection of points on the screen remote from the menu, and data entry at those points.
For this class of tasks it is common to use an analog pointing device, for example, a mouse, which is located on a separate surface immediately adjacent to a discrete binary keyboard input device. The analog pointing device is moved around on the surface and a cursor is correspondingly moved around a computer screen.
Since the analog pointing device is not in the primary area of the keyboard, the operator is required to move his/her hand back and forth between the keyboard and the pointing device, with significant resulting delay and distraction.
In order to reduce the time involved in the back and forth motion of an operator's hand between the typing keyboard and the analog pointing device, various approaches for combining the typing keyboard and the pointing device have been proposed. One such approach involves the dual use of standard keys on the keyboard as cursor control keys. In order to tell the standard keys to function as cursor control keys, a mode control switch, such as a SHIFT key, had to be hit. If the mode control switch was not hit, then the keys would operate in a normal manner to input an appropriate character into the computer. This approach proved unsatisfactory in the art because of the mental load imposed on an operator in remembering which standard keys will perform which cursor control operation.
Once the above-mentioned approach was abandoned, separate cursor control keys became almost universal. However, with the separate cursor control keys, only limited cursor control can be accomplished, as compared to using a mouse, since the cursor control keys operate in a discrete binary manner.
Another approach involved an analog input device located within or immediately adjacent to the standard keyboard area, but located separate from the standard keys. Within this class are various proposed and commercial devices intended to be operated by the thumb, and located below the space bar. A common restriction on all of these devices is the severely limited space available in the standard keyboard area.
The next step of development involved placing sensors, such as strain gauge sensors, adjacent to a particular standard key on the keyboard as described in U.S. Pat. No. 4,680,577 to Straayer et al. With such an arrangement, when the key is pressed in a normal direction, i.e., vertically downwards and perpendicular to the key cap surface, the key performs its normal function of inputting a specific character. However, if the key is moved horizontally or vertically, i.e., parallel to the key cap surface, then the strain gauge sensors sense such motion and the cursor is correspondingly moved on the screen.
A problem, however, has existed with respect to the analog input device constructed in accordance with the U.S. Patent cited above. Specifically, a different key structure must be substituted for an original key structure in order to use the key as both a data entry device and an analog pointing device. More specifically, a key structure which enables the use of the required sensors is needed. Thus, it is difficult to retrofit an existing keyboard to make use of the cursor control function. Another problem with this device is that only two degrees of freedom, that is, vertical and horizontal (y and x), of the key are allowed to be sensed. Furthermore, the cursor is constrained to be controlled only by a data entry key.